Imaging Agents

Magnetic resonance Imaging (MRI) produces tomographic images of the human body by interrogating the magnetism of hydrogen nuclei (protons) within the body’s tissues. Light and dark regions are depicted on the images depending on different physical properties of protons in different tissues. The MRI scanner could measure and report quantities like proton density, however this results in relatively low contrast since tissues often have very similar proton density. Instead, the scanner typically measures the rate the protons disturbed from their equilibrium orientation will return to that equilibrium state, so-called relaxation rates.

Nearly one-third of all scans performed in the US do not rely only on the naturally occurring differences in relaxation rates. Imaging agents are non-toxic substances that can be introduced into the body to accentuate differences between protons in different regions in order to highlight certain body structures or processes. The most commonly employed imaging agents are gadolinium chelates, compounds that markedly speed up the relaxation rates of protons with which they come into contact. Sequential images can trace the introduction of these imaging agents into the body and follow their distribution through the heart, the bloodstream, and the major organs. Detailed measurements, for example of the rate that these contrast agents can seep across membranes, reveal modifications of tissues that can be indications of malignancies.

Hyperpolarized gases MagniXene™ and MagniLium™ operate differently. Rather than modify the signal from protons, each provides a separate, unique signal that can be introduced, manipulated, and interrogated with MRI. Both offer outstanding capability and flexibility for imaging the lung air spaces. Because xenon is soluble in tissues, MagniXene™ has potential applications that extend beyond the gas space.

Imaging agents are classified by the US Food and Drug Administration (FDA) as drugs. Consequently they must pass through the regulatory mechanism of Phase I, II and III approval, demonstrating safety, efficacy, and superiority. The National Institutes of Health devotes attention and resources towards smoothing the transition and easing the burden of regulatory approval of new and promising drugs. Also the US Congress has carved out an exemption to the US Trademark and Patent Act, the FDA safe harbor laws, to hold harmless all efforts related to regulatory approval as non-infringing activities. Xemed is pursuing FDA approval of MagniXene™ and MagniLium™ within the FDA safe harbor framework.